texture.c

学习c++必备

/*
 * chess.c - part of the chess demo in the glut distribution.
 *
 * (C) Henk Kok ([e-mail])
 *
 * This file can be freely copied, changed, redistributed, etc. as long as
 * this copyright notice stays intact.
 */

/*
 * Marble texture - shamelessly ripped from siggraph92_C23.shar
 */

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <GL/glut.h>
#include "chess.h"

#define DOT(a,b) (a[0] * b[0] + a[1] * b[1] + a[2] * b[2])

#define B 256

static int p[B + B + 2];
static GLfloat g[B + B + 2][3];
static int start = 1;

#define setup(i,b0,b1,r0,r1) \
        t = vec[i] + 10000.; \
        b0 = ((int)t) & (B-1); \
        b1 = (b0+1) & (B-1); \
        r0 = t - (int)t; \
        r1 = r0 - 1.;

GLfloat noise3(GLfloat vec[3])
{
        int bx0, bx1, by0, by1, bz0, bz1, b00, b10, b01, b11;
        GLfloat rx0, rx1, ry0, ry1, rz0, rz1, *q, sx, sy, sz, a, b, c, d, t, u, v;
        register int i, j;

        if (start) {
                start = 0;
                init();
        }

        setup(0, bx0,bx1, rx0,rx1);
        setup(1, by0,by1, ry0,ry1);
        setup(2, bz0,bz1, rz0,rz1);

        i = p[ bx0 ];
        j = p[ bx1 ];

        b00 = p[ i + by0 ];
        b10 = p[ j + by0 ];
        b01 = p[ i + by1 ];
        b11 = p[ j + by1 ];
#define at(rx,ry,rz) ( rx * q[0] + ry * q[1] + rz * q[2] )

#define surve(t) ( t * t * (3. - 2. * t) )

#define lerp(t, a, b) ( a + t * (b - a) )

        sx = surve(rx0);
        sy = surve(ry0);
        sz = surve(rz0);


        q = g[ b00 + bz0 ] ; u = at(rx0,ry0,rz0);
        q = g[ b10 + bz0 ] ; v = at(rx1,ry0,rz0);
        a = lerp(sx, u, v);

        q = g[ b01 + bz0 ] ; u = at(rx0,ry1,rz0);
        q = g[ b11 + bz0 ] ; v = at(rx1,ry1,rz0);
        b = lerp(sx, u, v);

        c = lerp(sy, a, b);          /* interpolate in y at lo x */

        q = g[ b00 + bz1 ] ; u = at(rx0,ry0,rz1);
        q = g[ b10 + bz1 ] ; v = at(rx1,ry0,rz1);
        a = lerp(sx, u, v);

        q = g[ b01 + bz1 ] ; u = at(rx0,ry1,rz1);
        q = g[ b11 + bz1 ] ; v = at(rx1,ry1,rz1);
        b = lerp(sx, u, v);

        d = lerp(sy, a, b);          /* interpolate in y at hi x */

        return 1.5 * lerp(sz, c, d); /* interpolate in z */
}

void
init(void)
{
    int i, j, k;
    GLfloat v[3], s;

/* Create an array of random gradient vectors uniformly on the unit sphere */

    srand(1);
    for (i = 0 ; i < B ; i++) {
	do {		/* Choose uniformly in a cube */
	    for (j=0 ; j<3 ; j++)
		v[j] = (GLfloat)((rand() % (B + B)) - B) / B;
	    s = DOT(v,v);
	} while (s > 1.0);	  /* If not in sphere try again */
	s = sqrt(s);
	for (j = 0 ; j < 3 ; j++)       /* Else normalize */
	    g[i][j] = v[j] / s;
    }

/* Create a pseudorandom permutation of [1..B] */

    for (i = 0 ; i < B ; i++)
	p[i] = i;
    for (i = B ; i > 0 ; i -= 2) {
	k = p[i];
	p[i] = p[j = rand() % B];
	p[j] = k;
    }

/* Extend g and p arrays to allow for faster indexing */

    for (i = 0 ; i < B + 2 ; i++) {
	p[B + i] = p[i];
	for (j = 0 ; j < 3 ; j++)
	    g[B + i][j] = g[i][j];
    }
}

GLfloat turbulence(GLfloat x, GLfloat y, GLfloat z, GLfloat lofreq, GLfloat hifreq)
{
    GLfloat freq, t, p[3];

    p[0] = x + 123.456;
    p[1] = y;
    p[2] = z;

    t = 0;
    for (freq = lofreq ; freq < hifreq ; freq *= 2.) {
	t += fabs(noise3(p)) / freq;
	p[0] *= 2.;
	p[1] *= 2.;
	p[2] *= 2.;
    }
    return t - 0.3; /* readjust to make mean value = 0.0 */
}

GLfloat marble(GLfloat x, GLfloat y, GLfloat z)
{
    GLfloat m;
    m = turbulence(x, y, z, 0.3, 400.0);
    if (m > 1.0)
	m = 1.0;
    if (m < 0.0)
	m = 0.0;
    return m;
}

extern GLubyte white_square[TXSX][TXSY][3];
extern GLubyte black_square[TXSX][TXSY][3];
extern GLubyte wood[TXSX][TXSY][3];

void GenerateTextures(void)
{
    int i,j,k;
    GLfloat x,y,t,w,b;
    for (i=0;i<TXSX;i++)
    {
	for (j=0;j<TXSY;j++)
	{
	    x = ((GLfloat) i)/20.0;
	    y = ((GLfloat) j)/20.0;
	    t = marble(x, y, 0.0);

	    t = 0.2 + t;
	    if (t > 1.0)
		t = 1.0;

	    wood[i][j][0] = (0.6*t)*255;
	    wood[i][j][1] = (0.4*t)*255;
	    wood[i][j][2] = (0.5-0.4*t)*255;

	    x = ((GLfloat) i)/20.0;
	    y = ((GLfloat) j)/20.0;
	    t = marble(x, y, 0.0);

	    t = 0.2 + t;
	    if (t > 1.0)
		t = 1.0;

	    w = t;
	    b = 0.8 -t;
	    if (b < 0.0 )
		b = 0.0;

	    for (k=0;k<3;k++)
	    {
		white_square[i][j][k] = w*255;
		black_square[i][TXSY-j][k] = b*255;
	    }
	}
    }
}